See this guide’s sections
Other options for using WoS data
Other options for using Scopus data
Other options for using Dimensions data
In addition to the actual citation databases, other machine-readable interfaces with metadata that includes citation information are Crossref API and DataCite API, which register DOI identifiers. These are both free, openly available applications that do not necessarily even require registration or authentication. However, giving a contact address when making a UI request is considered polite, and polite requests are given priority. As the Initiative for Open Citations collaboration has grown more expansive, the citation data of a large proportion of all publications that have received a DOI is publicly available in the metadata of DOI registers, which also gives up-to-date information on the number of citations received by the publication.
However, the interfaces of DOI registers are primarily created for retrieving the metadata of publications, and not so much for compiling publication metrics data. Even though they offer the opportunity to search for publications by the author’s name, for example, or using the terms of a certain metadata field, the search functions are, for now, less refined than those of actual citation database interfaces. The response times of more complex or larger searches may also be longer.